Not all cameras seem to have the facility of resetting lens focus to infinity? I must admit I have not seen or investigated this possibility with my G3.

I am pretty sure the G3 will reset the lens too, both when you mount a new lens, and when you turn the camera on after it's been off. Both my G1 and my E-M5 does it, and I think all MFT cameras do this by default (although at least some may have an option of disabling it). If you have the 20, you can easily see this for yourself since its AF is visible as well as audible. Doesn't it perform a little dance where it moves the inner barrel in-out every time you mount it or turn the camera on?

This dance happens all right, but I will have to check what position the focus gets to after turning on again. I don't have the lens with me. Does it go back to where it was before turning off or does it go to infinity by default and forget where it was at turning off? If the latter then the awful delays I remember must have been when I used the lens for close focus.

A lot of the impression of nimbleness from slow zooms may be from their being slow and thus not needing to sweep the aperture too much.